This invention relates to systems and processes for treatment of a waste stream in a generally biological process for conversion of organic and inorganic pollutants into biomass and other products. The new system and process introduces waste activated sludge into the influent waste stream received by a waste stream treatment system that may be mixed in an anaerobic contact process. The anaerobic contact process may be in fluid communication with a solids separation process for separation of the biomass and particulate matter to produce a treated process effluent.
Activated sludge processes are one of the most commonly used wastewater treatment processes in which organic and inorganic pollutants are converted into particulate biomass suspended in fluid in an aeration process. The particulate biomass may then be separated from the fluid to produce a concentrated activated sludge and an effluent. The concentrated activated sludge may be returned to the aeration process as return activated sludge to be mixed with the waste stream influent. A portion of the concentrated activated sludge may be wasted from the process to maintain an optimal concentration of system biomass. The activated sludge process may require a large energy input as the process may be based on aeration conditions to the extent that the activated sludge process may consume significant energy in a wastewater treatment plant.
The waste activated sludge may be subjected to further treatment and/or disposed. Often waste activated sludge may be processed in an anaerobic digestion process that may produce methane gas. The energy in the methane gas may be captured using boilers or energy systems. This energy may be used to reduce energy supply requirements of the treatment process.
Rather than simply processing the waste activated sludge for disposal, the present invention discloses that the waste activated sludge may be used to process influent wastewater in an anaerobic contact process in combination with the waste activated sludge. To the extent this process is efficient in wastewater treatment it may reduce the aeration energy requirements and thereby the overall wastewater treatment facility energy requirements. The use of the waste activated sludge anaerobic contact process may also reduce the wastewater treatment facility size requirement as well as result in an increased potential for energy recovery through anaerobic digestion due to a higher energy content in the resultant waste sludge.